Conventionally, rotary parts feeders making use of vibration have been widely used for arranging the orientation of component parts.
In a rotary parts feeder, components parts are guided along a spiral path defined on the inner surface of a bowl and moved along the path by being subjected to vibrations. A gate provided in the spiral path allows the passage of only those component parts that are oriented in a proper manner while those oriented in any other improper orientations are thrown off the spiral path so that the component parts having a uniform attitude are fed out of the parts feeder.
However, according to such a parts feeder, as it only allows the passage of properly oriented component parts while throwing those oriented in any improper manner back into the bowl, only a part of the component parts moving along the spiral path are allowed to be fed out of the parts feeder, and the efficiency of the feeding action is therefore substantially poor. Therefore, in assembly lines involving relatively high line speeds, it is often necessary to arrange a number of parts feeders in a parallel relationship for a single assembling machine.
Furthermore, because the improperly oriented component parts are thrown back into the bowl, and are again fed along the feeding path, the possibility of damaging the component parts is increased due to the increased dwell time of the component parts in the feeding path.
Normally, a component part which is required to be properly oriented when being fed has at least two stable orientations, and is not completely symmetric. Therefore, when the component part is placed in an intermediate orientation between these two stable orientations, its center of gravity is offset to one side, and the component part tends to change its orientation to one of the at least two orientations under the action of gravity.